U.S. patent number 7,108,493 [Application Number 10/474,225] was granted by the patent office on 2006-09-19 for variable displacement pump having rotating cam ring.
This patent grant is currently assigned to Argo-Tech Corporation. Invention is credited to Martin A. Clements, Lowell D. Hansen.
United States Patent |
7,108,493 |
Clements , et al. |
September 19, 2006 |
Variable displacement pump having rotating cam ring
Abstract
Vane pump (10) mechanical losses are reduced by removing vane
friction losses and replacing them with lower magnitude journal
bearing fluid film viscous drag losses. A freely rotating cam ring
(70) is supported by a journal bearing (80). A relatively low
sliding velocity is imposed between the cam ring and the vanes
(26). This permits the use of less expensive and less brittle
materials in the pump by allowing the pump to operate at much
higher speeds without concern for exceeding vane tip velocity
limits.
Inventors: |
Clements; Martin A. (North
Royalton, OH), Hansen; Lowell D. (Sagamore Hills, OH) |
Assignee: |
Argo-Tech Corporation
(Cleveland, OH)
|
Family
ID: |
32713694 |
Appl.
No.: |
10/474,225 |
Filed: |
March 27, 2002 |
PCT
Filed: |
March 27, 2002 |
PCT No.: |
PCT/US02/09298 |
371(c)(1),(2),(4) Date: |
October 03, 2003 |
PCT
Pub. No.: |
WO02/081921 |
PCT
Pub. Date: |
October 17, 2002 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040136853 A1 |
Jul 15, 2004 |
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Current U.S.
Class: |
418/30; 418/1;
418/152; 418/173; 418/31 |
Current CPC
Class: |
F04C
2/344 (20130101); F04C 2/348 (20130101); F04C
14/226 (20130101); F04C 2230/604 (20130101); Y10T
29/49245 (20150115); F04C 2230/00 (20130101) |
Current International
Class: |
F03C
2/00 (20060101); F04C 14/18 (20060101) |
Field of
Search: |
;418/1,30,31,152,173 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
33 33 647 |
|
May 1984 |
|
DE |
|
33 07 099 |
|
Sep 1984 |
|
DE |
|
88 14 553 |
|
Mar 1990 |
|
DE |
|
40 11 671 |
|
Oct 1991 |
|
DE |
|
42 01 257 |
|
Jul 1993 |
|
DE |
|
44 28 410 |
|
Feb 1996 |
|
DE |
|
198 47 275 |
|
Mar 2000 |
|
DE |
|
199 57 886 |
|
Jul 2000 |
|
DE |
|
100 04 028 |
|
Aug 2000 |
|
DE |
|
199 15 739 |
|
Oct 2000 |
|
DE |
|
101 20 252 |
|
Jan 2002 |
|
DE |
|
0 049 838 |
|
Apr 1982 |
|
EP |
|
0 095 194 |
|
Nov 1983 |
|
EP |
|
0 135 091 |
|
Mar 1985 |
|
EP |
|
0 171 182 |
|
Feb 1986 |
|
EP |
|
0 171 183 |
|
Feb 1986 |
|
EP |
|
0 210 786 |
|
Feb 1987 |
|
EP |
|
1 043 504 |
|
Oct 2000 |
|
EP |
|
2195271 |
|
Mar 1974 |
|
FR |
|
2802983 |
|
Jun 2001 |
|
FR |
|
687998 |
|
Feb 1953 |
|
GB |
|
572736 |
|
Oct 1956 |
|
GB |
|
984255 |
|
Feb 1965 |
|
GB |
|
1224265 |
|
Mar 1971 |
|
GB |
|
1328728 |
|
Aug 1973 |
|
GB |
|
1341414 |
|
Dec 1973 |
|
GB |
|
1341415 |
|
Dec 1973 |
|
GB |
|
1 374 597 |
|
Nov 1974 |
|
GB |
|
1 435 556 |
|
May 1976 |
|
GB |
|
2016087 |
|
Sep 1979 |
|
GB |
|
2 026 094 |
|
Jan 1980 |
|
GB |
|
2 074 274 |
|
Oct 1981 |
|
GB |
|
2 126 657 |
|
Mar 1984 |
|
GB |
|
2313092 |
|
Jun 1984 |
|
GB |
|
2 151 705 |
|
Jul 1985 |
|
GB |
|
2 167 811 |
|
Jun 1986 |
|
GB |
|
2 185 535 |
|
Jul 1987 |
|
GB |
|
59 188077 |
|
Oct 1984 |
|
JP |
|
WO 90/08900 |
|
Aug 1990 |
|
WO |
|
WO 00/20760 |
|
Apr 2000 |
|
WO |
|
WO 01/65118 |
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Sep 2001 |
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WO |
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Primary Examiner: Trieu; Theresa
Attorney, Agent or Firm: Fay, Sharpe, Fagan, Minnich &
McKee, LLP
Claims
The invention claimed is:
1. A variable displacement gas turbine fuel pump comprising: a
housing having a pump chamber, and an inlet and outlet in fluid
communication with the pump chamber; a rotor received in the pump
chamber; a cam member surrounding the rotor and freely rotating
relative to the housing; a cam sleeve radially interposed between
the cam member and the housing; means for altering a position of
the cam sleeve in the housing to selectively vary pump output; a
spacer ring radially interposed between the cam sleeve and the
housing wherein the spacer ring includes a generally planar cam
sleeve rolling surface that allows a centerpoint of the cam sleeve
to linerarly translate; and a journal bearing interposed between
the cam member and the cam sleeve for reducing mechanical losses
during operation of the pump.
2. The fuel pump of claim 1 wherein the cam member has a smooth,
inner peripheral wall that allows the rotor to rotate freely
relative to the cam member.
3. The fuel pump of claim 1 wherein the journal bearing is a
continuous annular passage between the cam member and the cam
sleeve.
4. The fuel pump of claim 1 further comprising circumferentially
spaced vanes operatively associated with the rotor.
5. The fuel pump of claim 1 wherein the journal bearing is a
hydrostatic bearing.
6. The fuel pump of claim 1 wherein the journal bearing is a
hydrodynamic bearing.
7. The fuel pump of claim 1 wherein the journal bearing is a hybrid
hydrostatic/hydro dynamic bearing.
8. A variable displacement gas turbine fuel pump for supplying jet
fuel from a supply to a set of downstream nozzles, the gas turbine
fuel pump comprising: a housing having a fuel inlet and a fuel
outlet in operative communication with a pump chamber; a rotor
received in the pump chamber, the rotor having plural vanes that
segregate the pump chamber into individual pump chamber portions; a
cam ring received around the rotor having radially inner and outer
surfaces, the inner surface slidingly engaging the vanes; a cam
sleeve radially interposed between the cam ring and the housing; a
spacer ring radially interposed between the cam sleeve and the
housing, the cam sleeve being secured to the spacer ring to
selectively vary eccentricity between the cam ring and the rotor;
means for altering a position of the cam sleeve in the housing to
selectively vary pump output; and a cam journal bearing surrounding
the cam ring in communication with the fuel inlet whereby jet fuel
serves as the fluid film in the journal bearing for the cam ring,
wherein the journal bearing is a continuous annular passage between
the cam ring and the cam sleeve.
9. The fuel pump of claim 8 wherein the journal bearing is a
hydrodynamic bearing.
10. The fuel pump of claim 8 wherein the journal bearing is a
hydrostatic bearing.
11. The fuel pump of claim 8 wherein the journal bearing is a
hybrid hydrostatic/hydrodynamic bearing.
12. The fuel pump of claim 8 wherein a center of the cam sleeve
enclosing the cam ring is selectively offset from a rotational axis
of the rotor.
13. The fuel pump of claim 8 further comprising circumferentially
spaced vanes operatively associated with the rotor.
14. The fuel pump of claim 8 wherein the vanes are formed of
tungsten carbide.
15. The fuel pump of claim 8 wherein the cam ring is formed of a
low cost, durable material.
16. A method of operating a gas turbine fuel pump that includes a
housing having a pump chamber that receives a rotor therein and a
cam member surrounding the rotor, a cam sleeve surrounding the cam
member and a spacer ring disposed between the cam sleeve and the
housing, a generally planar cam rolling surface along an inner
surface thereof adjacent an anti-rotation pin interconnecting the
spacer ring and the cam sleeve, and upon which the cam sleeve rolls
in response to actuation of the altering means, the method
comprising the steps of: supporting the cam member via a journal
bearing disposed between the cam member and the cam sleeve in the
housing; allowing the rotor to rotate freely relative to the cam
member; and linearly translating a centerpoint of the cam sleeve to
limit pressure pulsations in seal zones of the assembly.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a pump, and more specifically to a
high-speed vane pump that finds particular use in fuel pumps,
metering, and control for jet engines.
Current vane pumps use one or more stationary, or non-rotating, cam
rings. Outer radial tips of the vanes slide along the cam rings.
The rings are not, however, free to rotate relative to the housing.
The stationary cam rings are rigidly fixed to a pump housing in a
fixed displacement pump, or the cam ring moves or pivots to provide
variable displacement capability. Thus, as will be-appreciated by
one skilled in the art, these types of positive displacement pumps
include a stator or housing having inlet and outlet ports,
typically at locations diametrically offset relative to an axis of
rotation of a rotor received in a pump chamber. Plural,
circumferentially spaced and radially extending guides or vanes
extend outwardly from the rotor. Since the rotor axis is offset and
parallel to an axis of the housing chamber, the offset relationship
of the axes causes the vanes to move radially inward and outward
relative to the rotor during rotation.
Outer tips of the vanes contact the cam ring and the contact forces
of the individual vanes, usually numbering from six to twelve,
impose frictional drag forces on the cam ring. These drag forces
convert directly into mechanical losses that reduce the overall
efficiency of the pump. In many applications, these mechanical drag
losses far exceed the theoretical power to pump the fluid.
When used in the jet engine environment, for example, vane pumps
use materials that are of generally high durability and wear
resistance due to the high velocity and loading factors encountered
by these vane pumps. Parts manufactured from these materials
generally cost more to produce and suffer from high brittleness.
For example, tungsten carbide is widely used as a preferred
material for vane pump components used in jet engines. Tungsten
carbide is a very hard material that finds particular application
in the vane, cam ring, and side plates. However, tungsten carbide
is approximately two and one-half (21/2) times the cost of steel,
for example, and any flaw or overstress can result in cracking and
associated problems. In addition, the ratio of the weight of
tungsten carbide relative to steel is approximately 1.86 so that
weight becomes an important consideration for these types of
applications. Thus, although the generally high durability and wear
resistance make tungsten carbide suitable for the high velocity and
loading factors in vane pumps, the weight, cost, and high
brittleness associated therewith results in a substantial increase
in overall cost.
Even using special materials such as tungsten carbide, current vane
pumps are somewhat limited in turning speed. The limit relates to
the high vane tip sliding velocity relative to the cam ring. Even
with tungsten carbide widely used in the vane pump, high speed pump
operation over 12,000 RPM is extremely difficult.
Improved efficiencies in the pump are extremely desirable, and
increased efficiencies in conjunction with increased reliability
and the ability to use a vane-type pump for other applications are
desired.
SUMMARY OF THE INVENTION
An improved gas turbine fuel pump exhibiting increased efficiency
and reliability is provided by the present invention.
More particularly, the gas turbine fuel pump includes a housing
having a pump chamber and an inlet and outlet in fluid
communication with the chamber. A rotor is received in the pump
chamber and a cam member surrounds the rotor and is freely
rotatable relative to the housing.
A journal bearing is interposed between the cam member and the
housing for reducing mechanical losses during operation of the
pump.
The journal bearing is a continuous annular passage defined between
the cam member and the housing.
The rotor includes circumferentially spaced vanes having outer
radial tips in contact with the cam member.
The pump further includes a cam sleeve pivotally secured within the
housing to selectively vary the eccentricity between the cam member
and the rotor.
The gas turbine fuel pump exhibits dramatically improved
efficiencies over conventional vane pumps that do not employ the
freely rotating cam member.
The fuel pump also exhibits improved reliability at a reduced cost
since selected components can be formed of a reasonably durable,
less expensive material.
The improved efficiencies also permit the pump to be smaller and
more compact which is particularly useful for selected applications
where size is a critical feature.
Still other benefits and advantages of the invention will become
apparent to one skilled in the art upon reading the following
detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of a preferred embodiment of
the fluid pump.
FIG. 2 is a cross-sectional view through the assembled pump of FIG.
1.
FIG. 3 is a longitudinal cross-sectional view through the assembled
pump.
FIG. 4 is a cross-sectional view similar to FIG. 2 illustrating a
variable displacement pump with the support ring located in a
second position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in the Figures, a pump assembly 10 includes a housing 12
having a pump chamber 14 defined therein. Rotatably received in the
chamber is a rotor 20 secured to a shaft 22 for rotating the rotor
within the chamber. Peripherally or circumferentially spaced about
the rotor are a series of radially extending grooves 24 that
operatively receive blades or vanes 26 having outer radial tips
that extend from the periphery of the rotor. The vanes may vary in
number, for example, nine (9) vanes are shown in the embodiment of
FIG. 2, although a different number of vanes can be used without
departing from the scope and intent of the present invention. As is
perhaps best illustrated in FIG. 2, the rotational axis of the
shaft 22 and rotor 20 is referenced by numeral 30. Selected vanes
(right-hand vanes shown in FIG. 2) do not extend outwardly from the
periphery of the rotor to as great an extent as the remaining vanes
(left-hand vanes in FIG. 2) as the rotor rotates within the housing
chamber. Pumping chambers are defined between each of the vanes as
the vanes rotate in the pump chamber with the rotor and provide
positive displacement of the fluid.
With continued reference to FIG. 2, a spacer ring 40 is rigidly
secured in the housing and received around the rotor at a location
spaced adjacent the inner wall of the housing chamber. The spacer
ring has a flat or planar cam rolling surface 42 and receives an
anti-rotation pin 44. The pin pivotally receives a cam sleeve 50
that is non-rotatably received around the rotor. First and second
lobes or actuating surfaces 52, 54 are provided on the sleeve,
typically at a location opposite the anti-rotation pin. The lobes
cooperate with first and second actuator assemblies 56, 58 to
define means for altering a position of the cam sleeve 50. The
altering means selectively alter the stroke or displacement of the
pump in a manner well known in the art. For example, each actuator
assembly includes a piston 60, biasing means such as spring 62, and
a closure member 64 so that in response to pressure applied to a
rear face of the pistons, actuating lobes of the cam sleeve are
selectively moved. This selective actuation results in rolling
movement of the cam sleeve along a generally planar or flat surface
66 located along an inner surface of the spacer ring adjacent on
the pin 44. It is desirable that the cam sleeve undergo a linear
translation of the centerpoint, rather than arcuate movement, to
limit pressure pulsations that may otherwise arise in seal zones of
the assembly. In this manner, the center of the cam sleeve is
selectively offset from the rotational axis 30 of the shaft and
rotor when one of the actuator assemblies is actuated and moves the
cam sleeve (FIG. 2). Other details of the cam sleeve, actuating
surface, and actuating assemblies are generally well known to those
skilled in the art so that further discussion herein is deemed
unnecessary.
Received within the cam sleeve is a rotating cam member or ring 70
having a smooth, inner peripheral wall 72 that is contacted by the
outer tips of the individual vanes 26 extending from the rotor. An
outer, smooth peripheral wall 74 of the cam ring is configured for
free rotation within the cam sleeve 50. More particularly, a
journal bearing 80 supports the rotating cam ring 70 within the
sleeve. The journal bearing is filled with the pump fluid, here jet
fuel, and defines a hydrostatic or hydrodynamic, or a hybrid
hydrostatic/hydrodynamic bearing. The frictional forces developed
between the outer tips of the vanes and the rotating cam ring 70
result in a cam ring that rotates at approximately the same speed
as the rotor, although the cam ring is free to rotate relative to
the rotor since there is no structural component interlocking the
cam ring for rotation with the rotor. It will be appreciated that
the ring rotates slightly less than the speed of the rotor, or even
slightly greater than the speed of the rotor, but due to the
support/operation in the fluid film bearing, the cam ring possesses
a much lower magnitude viscous drag. The low viscous drag of the
cam ring substitutes for the high mechanical losses exhibited by
known vane pumps that result from the vane frictional losses
contacting the surrounding stationary ring. The drag forces
resulting from contact of the vanes with the cam ring are converted
directly into mechanical losses that reduce the pumps overall
efficiency. The cam ring is supported solely by the journal bearing
80 within the cam sleeve. The journal bearing is a continuous
passage. That is, there is no interconnecting structural component
such as roller bearings, pins, or the like that would adversely
impact on the benefits obtained by the low viscous drag of the cam
ring. For example, flooded ball bearings would not exhibit the
improved efficiencies offered by the journal bearing, particularly
a journal bearing that advantageously uses the pump fluid as the
fluid bearing.
In prior applications these mechanical drag losses can far exceed
the mechanical power to pump the fluid in many operating regimes of
the jet engine fuel pump. As a result, there was a required use of
materials having higher durability and wear resistance because of
the high velocity and load factors in these vane pumps. The
material weight and manufacturing costs were substantially greater,
and the materials also suffer from high brittleness. The turning
speed of those pumps was also limited due to the high vane sliding
velocities relative to the cam ring. Even when using special
materials such as tungsten carbide, high speed pump operation,
e.g., over 12,000 RPM, was extremely difficult.
These mechanical losses resulting from friction between the vane
and cam ring are replaced in the present invention with much lower
magnitude viscous drag losses. This results from the ability of the
cam ring to rotate with the rotor vanes. A relatively low sliding
velocity between the cam ring and vanes results, and allows the
manufacturer to use less expensive, less brittle materials in the
pump. This provides for increased reliability and permits the pump
to be operated at much higher speeds without the concern for
exceeding tip velocity limits. In turn, higher operating speeds
result in smaller displacements required for achieving a given
flow. In other words, a smaller, more compact pump can provide
similar flow results as a prior larger pump. The pump will also
have an extended range of application for various vane pump
mechanisms.
FIG. 3 more particularly illustrates inlet and outlet porting about
the rotor for providing an inlet and outlet to the pump chamber.
First and second plates 90, 92 have openings 94, 96, respectively.
Energy is imparted to the fluid by the rotating vanes. Jet fuel,
for example, is pumped to a desired downstream use at an elevated
pressure.
As shown in FIG. 4, neither of the actuating assemblies is
pressurized so that the cam sleeve is not pivoted to vary the
stroke of the vane pump. That is, this no flow position of FIG. 4
can be compared to FIG. 2 where the cam sleeve 50 is pivoted about
the pin 44 so that a close clearance is defined between the cam
sleeve and the spacer ring 40 along the left-hand quadrants of the
pump as illustrated in the Figure. This provides for variable
displacement capabilities in a manner achieved by altering the
position of the cam sleeve.
In the preferred arrangement, the vanes are still manufactured from
a durable, hard material such as tungsten carbide. The cam ring and
side plates, though, are alternately formed of a low cost, durable
material such as steel to reduce the weight and manufacturing
costs, and allow greater reliability. Of course, it will be
realized that if desired, all of the components can still be formed
of more expensive durable materials such as tungsten carbide and
still achieve substantial efficiency benefits over prior
arrangements. By using the jet fuel as the fluid that forms the
journal bearing, the benefits of tungsten carbide for selected
components and steel for other components of the pump assembly are
used to advantage. This is to be contrasted with using oil or
similar hydraulic fluids as the journal bearing fluid where it
would be necessary for all of the jet fuel components to be formed
from steel, thus eliminating the opportunity to obtain the benefits
offered by using tungsten carbide.
The invention has been described with reference to the preferred
embodiments. Obviously, modifications and alterations will occur to
others upon reading and understanding the preceding detailed
description. It is intended that the invention be construed as
including all such modifications and alterations in so far as they
come within the scope of the appended claims or the equivalents
thereof.
* * * * *